Voter caging is a long-recognized, controversial Republican voter suppression tactic which has often been used to target minority voters in heavily Democratic precincts. It is a practice whereby a political party or campaign sends mail that can't be forwarded to a targeted group of registered voters—often minorities. A "caging list" of those whose mail is returned "undelivered" is then used as the basis for getting them taken off the voter rolls, on the grounds that the voter does not live at the address where he or she is registered. There is evidence that caging lists were assembled in Florida, Ohio and Pennsylvania during the 2004 elections, possibly intended as the basis for massive voter eligibility challenges. While the Senate recently unveiled a bill aimed at preventing the practice of voter caging, Republican officials maintain that voter caging is part of what they describe as "ballot security" measures necessary to combat voter fraud. So far, the Justice Department has failed to uncover significant evidence of widespread voter fraud in America.